Swapping Animal Products for Plant-Based Foods—No Matter How Processed—Leads to Weight Loss, Finds New Study

WASHINGTON, D.C.—Replacing animal products with plant-based foods, regardless of their level of processing, can lead to significant weight loss, according to new research by the Physicians Committee for Responsible Medicine published in the journal Nutrition & Metabolism.

“Our research shows that choosing a bagel instead of bacon for breakfast or a veggie burger instead of a hamburger for dinner is the best option if you are looking to lose weight,” says Hana Kahleova, MD, PhD, director of clinical research for the Physicians Committee for Responsible Medicine. “Filling your plate with plant-based foods—even if they are considered ultra-processed like soy milk and vegan meat and yogurt alternatives—instead animal products can have a positive impact on your weight and overall health.”

The new research is a secondary analysis of a study that randomly assigned participants who were overweight to an intervention or control group for 16 weeks. Participants in the intervention group followed a low-fat, plant-based diet with no calorie limit. The control group made no diet changes. In the study, those in the vegan group boosted their metabolism, lost weight, and improved cardiometabolic risk factors, compared to those in the control group.

The new analysis looked at the role processed foods played in the weight loss. The participants’ dietary records were analyzed, and all foods—both animal products and plant-based foods—were categorized using the NOVA system, which assigns foods to categories based on their level of processing. NOVA category 1 is defined as unprocessed or minimally processed foods; category 2 includes processed ingredients, such as salt, sugar, oil, and butter; category 3 includes processed foods made by adding salt, sugar, preservatives; and category 4 is composed of ultra-processed foods, greatly modified by industrial techniques and processes.

Study participants in the vegan group decreased consumption of animal products and increased plant-based foods in all four NOVA categories, which led to an average weight loss of 13 pounds (5.9 kilograms), compared to an insignificant change in the control group.

The top three predictors of weight loss were reduced consumption of processed animal foods (such as smoked fish), unprocessed or minimally processed animal foods (such as milk, beef, and eggs), and ultra-processed animal foods (such as cheese, fried chicken, and sausage).

This appears to have resulted from reduced calorie and fat intake and increased fiber intake, as well calorie burn from increased after-meal metabolism.

“Our new study is an important reminder that plant-based foods that are considered processed, like canned beans, cereal, and veggie burgers, are actually part of a healthy diet that can help fight America’s diet-related chronic disease epidemics,” says Dr. Kahleova.